Jelly Ear and other fungi growing on wood

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Jelly Ear (Auricularia auricula-judae)

Autumn 2013 was one of the best years for fungi in our area for a long while and although most of the fleshy toadstools have now disappeared, there are still some fungi to look out for on trees and logs. The Jelly Ears shown here were photographed this afternoon in the Pelenna Valley near Ton Mawr. Jelly Ear is usually associated with Elder (Sambucus nigra), but these were growing on Ash (Fraxinus excelsior). 

There are some fine Beech trees in the Gnoll Park (Neath), but these shallow-rooting trees often tumble over in high winds. So, over the years, the park has accumulated lots of beech logs and stumps that now support a variety of bracket fungi, such as Lumpy Bracket (photographed this morning near the First Pond). One of the conspicuous features of this bracket is the bright green bloom on its upper surface. This is an algal growth that is specifically associated with this bracket fungus and is a useful identification feature.

Lumpy Bracket (Trametes gibbosa)

Nearby, some Oyster Mushroom was also growing on an old Beech log.

  Oyster Mushroom (Pleurotus ostreatus)

Many fungi, like those shown here, use wood as a source of nutrients. Some bacteria can also do this, but otherwise this a very specialised skill in the natural world. Wood is mostly composed of cellulose and lignin, which are both polymers. Lignin has a low nutrient value, but cellulose (the most abundant organic compound on Earth) is a polymer of glucose, which is a high value nutrient. But cellulose does not give up its glucose easily and in order to access it, fungi (and bacteria) have to secrete special enzymes (cellulases) to unlock the cellulose chain. Fungi that specifically breakdown cellulose in wood are often called brown-rot fungi. However, many fungi can break down both lignin and cellulose and this results in a bleaching effect usually referred to as 'white-rot'. Some white-rot fungi are destructive parasites of living trees.